Alternative to the audio hack to disable background throttling?

[danburzo]

Electron version: 1.4.3

Hi there, we were going to use the audio hack to prevent the browser window from being throttled, but since the Electron app works on a Linode machine running Ubuntu, it throws an error about not finding any sound cards:

ALSA lib confmisc.c:768:(parse_card) cannot find card '0'
ALSA lib conf.c:4248:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory
ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings
ALSA lib conf.c:4248:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory
ALSA lib confmisc.c:1251:(snd_func_refer) error evaluating name
ALSA lib conf.c:4248:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
ALSA lib conf.c:4727:(snd_config_expand) Evaluate error: No such file or directory
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM default
ALSA lib confmisc.c:768:(parse_card) cannot find card '0'
ALSA lib conf.c:4248:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory
ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings
ALSA lib conf.c:4248:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory
ALSA lib confmisc.c:1251:(snd_func_refer) error evaluating name
ALSA lib conf.c:4248:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
ALSA lib conf.c:4727:(snd_config_expand) Evaluate error: No such file or directory
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM default

Installing a dummy audio card on a Linode machine seems extremely complicated (something about the Linode kernel not having the necessary features?), so I was wondering if anyone is aware of any alternative hacks to obtain the same result, without requiring a real/fake sound card.

Please note that neither webPreferences.backgroundThrottling, nor the disable-renderer-backgrounding work by themselves to prevent throttling.

Here's the mini test-case I'm using:

var app = require('electron').app;
var BrowserWindow = require('electron').BrowserWindow;

app.commandLine.appendSwitch("disable-renderer-backgrounding");

app.disableHardwareAcceleration();

var win, main, iteration = 0;

function leakke_li() {

    if (win) {
        win.destroy();
    }
    win = new BrowserWindow({
        width: 20000,
        height: 20000,
        webPreferences: {
            offscreen: true,
            backgroundThrottling: false
        },
        show: false
    });
    win.webContents.on('did-finish-load', function() {
        win.webContents.executeJavaScript(`(function(){
            // Start a silent audio source in the web page
            // to prevent it from being throttled in the background 
            // by an overzealous Chromium.
            // Reference: https://github.com/atom/atom/pull/9485/files
            var context = new AudioContext();
            var source = context.createBufferSource();
            source.connect(context.destination);
            source.start(0);
        })()`, function() {
            console.log('apply audio hack');
        });
        console.log('event:did-finish-load', ++iteration);
        win.webContents.once('paint', function(event, dirty, image) {
            console.log('event:paint');
            setTimeout(leakke_li, 300);
        });
        win.webContents.invalidate();
    });
    win.loadURL('about:blank');
}
app.on('ready', function() {
    var main = new BrowserWindow({ 
        width: 10, 
        height: 10, 
        webPreferences: {
            backgroundThrottling: false
        } 
    });
    leakke_li();
});

(It's a riff on the code in #7350)

---

Note for posterity: On a normal Ubuntu Server machine, getting a dummy sound card to make the Audio hack to work is as follows:

sudo apt-get install --reinstall linux-image-extra-`uname -r`
sudo modprobe snd-dummy

(With the caveat that I can provide no warranties about what it does to the machine, exercise caution. Reference)

---

Possible alternative?

On Mac, I've had some success with controlling the focus of the windows through window.focus() / app.focus(), but I'm not sure how focus management works with an Electron running with xvfb in a headless Ubuntu, so any pointers in this direction are much appreciated.

[zcbenz]

Can you try whether backgroundThrottling works in 1.3.x and 1.2x? It might be a regression.

[kevinsawicki]

Closing this out until more information is available.